Slack app for creating webhooks

app.rb

require 'sinatra'
require 'rest-client'
require 'json'

get '/oauth' do
  if params['code']

    options = {
      client_id: ENV['SLACK_CLIENT_ID'],
      client_secret: ENV['SLACK_CLIENT_SECRET'],
      code: params['code']
    }

    res = RestClient.post 'https://slack.com/api/oauth.access', options
    json = JSON.parse(res)

    if json["incoming_webhook"]
      p json["incoming_webhook"]["configuration_url"]
    else
      "Oh no! Something went wrong"
    end
  end
end

Gemfile.rb

source 'https://rubygems.org'
ruby "2.3.1"
gem 'sinatra'
gem 'rest-client'